The medical device industry produces a wide variety of electronic and mechanical devices suitable for use outside and inside the body for treating patient disease conditions. Devices used outside the body are termed external while devices used inside the body are termed implantable and include therapeutic substance infusion devices such as implantable drug pumps. Clinicians use medical devices alone or in combination with therapeutic substance therapies and surgery to treat patient medical conditions. For some medical conditions, medical devices provide the best, and sometimes the only, therapy to restore an individual to a more healthful condition and a fuller life. Implantable therapeutic substance infusion devices can be used to treat conditions such as pain, spasticity, cancer, and a wide variety of other medical conditions.
Implantable medical devices have important advantages over other forms of therapeutic substance administration. For example, oral administration is often not workable because the systemic dose of the substance needed to achieve the therapeutic dose at the target sight may be too large for the patient to tolerate without very adverse side effects. Also, some substances simply will not be absorbed in the gut adequately for a therapeutic dose to reach the target sight. Moreover, substances that are not lipid soluble may not cross the blood-brain barrier adequately if needed in the brain. In addition, infusion of substances from outside the body requires a transcutaneous catheter, which results in other risks such as infection or catheter dislodgement. Further, implantable medical devices avoid the problem of patient noncompliance, namely the patient failing to take the prescribed drug or therapy as instructed.
Implantable medical devices are often used in conjunction with various computer and telecommunication systems and components. Information obtained by the implantable medical device may be stored and subsequently transmitted to a physician or patient caregiver or a database on demand or automatically. Many ways of using the information are known including decision making to provide optimum medical care to the person with the medical condition.
An implantable therapeutic substance infusion device such as an implantable drug delivery device is implanted by a clinician into a patient at a location appropriate for the therapy that interferes as little as practicable with normal patient activity. This location is typically a subcutaneous region in the lower abdomen. The proximal or near end of the infusion catheter is connected to the drug pump infusion outlet. The catheter is simply a flexible tube with a lumen typically running the length of the catheter. The distal or far end of the catheter is positioned to infuse a drug or drug combination to a target site in the patient. Target sights in the body included but are not limited to an internal cavity, any blood vessel, any organ, or other tissue in the body. The drug or other therapeutic substance flows from the pump via the lumen in the catheter at a programmed infusion rate to treat the disease condition. The pump typically includes an expansible reservoir for containing a refillable supply of drug. For example, U.S. Pat. No. 4,692,147 (Duggan) and U.S. Pat. No. 5,445,616 (Kratoska et al) disclose types of implantable pumps that can be used.
Examples of diseases that are treatable include spasticity and chronic intractable pain. To treat spasticity, the distal tip of the catheter is typically surgically positioned in the intrathecal space of the patient's spinal column. Drug flows out of the distal tip into the cerebral spinal fluid where it baths the spinal cord. By virtue of molecular action on nervous tissue in the spinal cord, the patient's spasticity symptoms are dramatically reduced and the patient becomes much more comfortable and competent. Pain patients are treated in much the same way.
The infusion rate of the drug pump is typically programmed to be variable over time. The rate is usually controlled by certain components in the pump. The controlled infusion rate is often further set by using an external device or programmer to transmit into the pump, instructions for the controlled infusion. The controlled infusion may be variable as time passes according to the needs of the patient. The instructions provided to the pump to control the infusion rate of the drug pump are typically determined by a medical person. In some cases the patient is able to provide the instructions to the pump via an external patient-programming device. In contrast, fixed rate pumps usually cannot be programmed and are only capable of constant infusion rate.
Once implanted, the implantable medical device will require re-programming to account for changes in the desired therapy, changes in the condition being treated, or changes in the placement of the lead delivering the therapy to the body. This can be accomplished in any number of ways including, for example, the patient may manually adjust the treatment therapy, or the treating physician may manually adjust or re-program the implanted device. In either of these cases, there is no mechanism by which the implanted device may automatically make therapy adjustments or store prior therapy changes for later use and analysis.
It is therefore desirable to provide an implantable therapy delivery system that is capable of automatically making therapy adjustments. It is also desirable to provide an implantable therapy delivery system that provides historical information relating to the therapy changes made to the implanted devices.